Wireless telecommunications networks are known. In a cellular system radio coverage is provided by regions of geographical area. Those regions are known as cells. A base station is located in each cell to provide the radio coverage. Traditional base stations provide coverage in relatively large geographical areas and the cells are often referred to as macro cells. It is possible to provide smaller sized cells within a macro cell. Cells that are smaller than macro cells are sometimes referred to as micro cells, pico cells, or femto cells. However, throughout this document the term femto cell is used generically for cells that are smaller than macro cells. One way to establish a femto cell (sometimes referred to as a home cell) is to provide a femto base station (or home base station) that provides coverage having a relatively limited range within the coverage area of a macro cell. The transmission power of a femto base station is relatively low and, hence, each femto cell provides a small coverage area compared to that of a macro cell and covers, for example, an office or a home.
Such femto cells may be provided where the communications coverage provided by the macro cell is poor or where a user wishes to use an alternative communications link provided locally, by the femto base station, to communicate with the core network. Such a situation might arise where, for example, a user has a pre-existing communications link and the user wishes to utilise that link in preference to that provided by a macro cell network provider to communicate with the core network.
In order to maintain a high level of service to an end user, with minimal service interruption, it may be necessary to handover the user equipment from the macro cell within which it is located to a femto base station. Likewise, it may be necessary to handover the user equipment from one femto base station to another. However, there may be typically tens of thousands of femto base stations which may be deployed within a network under one controller. This presents a problem of identifying which femto base station to handover the user equipment to.
Accordingly, it is desired to provide an improved technique to enable handover to occur efficiently.